Good question, seeing how I have the 1 storage compartment that is the right size it allows for an interior bathroom, a step tub and a place to put a portable toilet. I do not want to have permanent waste tanks, just a portable waste tank. This simplifies the waste water system. Also by placing the bathroom in this location, on the other side (inside) will be a counter top for the sink/stove top combo. As I had shown in another a picture above there is a place where I will need to build a floor extension and can incorporate a fresh water tank in this area. So If you are following closely everything water related will be on the same side on the vehicle. Simple and easy.

I'm okay with the bathroom/shower combo, however I fail to see how having a portable waste system is going to simplifiy the waste water system. A hard mounted tank is set it and forget it simple. You never have to worry about making sure its secured, hoses hooked up, ect.